Manufacturing of integrated circuits involves deposition of various materials onto substrates. These materials include metal and metal-containing layers that can, for example, include diffusion barriers/liners that prevent diffusion of copper conducting layers (Cu) into dielectric materials and promote adhesion and growth of the Cu layers. Chemical vapor deposition (CVD) has seen increasing use for preparation of layers and coatings in semiconductor wafer processing. CVD is a favored deposition method in many respects, for example, because of its ability to provide highly conformal and high quality layers at relatively fast processing times. Further, CVD is beneficial in coating substrates of irregular shapes including the provision of highly conformal layers even with respect to deep contacts and other openings. In general, CVD techniques involve the delivery of gaseous reactants (precursors) to the surface of a substrate where chemical reactions take place under temperature and pressure conditions that are favorable to the thermodynamics of the desired reaction. The type and composition of layers that can be formed using CVD is limited by the ability to deliver the reactants to the surface of the substrate.
In order for device manufacturing process to be practical, the deposition processes need to be carried out in a reasonable amount of time while achieving relatively constant substrate throughput. This requirement can necessitate efficient delivery of a precursor containing the metal element from a precursor container to a process chamber containing the substrate(s) to be processed. A common problem encountered in the deposition of materials by CVD techniques are low deposition rates due to low vapor pressures of the precursors and the transport issues associated therewith, thereby making the deposition processes impractical. A low vapor pressure can limit the flow of the precursor from a precursor container through gas lines to a process chamber of a deposition system where a substrate is exposed to the precursor to deposit a layer on the substrate.
The delivery of solid or liquid precursors in CVD processing can be carried out using the sublimator/bubbler method in which the precursor is usually placed in a sublimator/bubbler container which is then heated to the vaporization temperature of the precursor. The heated precursor is vaporized into a gaseous compound that is transported into the process chamber with a carrier gas. However, this procedure has been unsuccessful in reliably and reproducibly vaporizing a solid precursor and delivering the vaporized precursor to the process chamber for a number of reasons. The major problems with the technique are centered on the inability to consistently vaporize a solid precursor at a controlled rate such that a reproducible flow of vaporized precursor can be delivered to the process chamber. Also it is difficult to ensure complete saturation of the fast moving carrier gas stream because of limited amount of exposed surface area of the solid precursor in the vaporizer system and lack of uniform temperature to provide maximum vaporization. In addition, the temperature to which the solid or liquid precursor can be heated to provide adequate vapor pressure can be limited by premature decomposition of the precursor at that temperature.
For these and other reasons, it is desirable to provide apparatus and methods for consistently vaporizing a solid precursor at a controlled rate and delivering the vaporized precursor to a process chamber that overcome the various problems associated with conventional vaporization systems.